<p>Вибери потрібне значення для <code>font</code>. У цьому прикладі, Ви можете змінювати такі властивості як <em>font-style</em>, <em>font-variant</em>, <em>font-weight</em>, <em>font-size</em>, <em>font-family</em> (у цій же послідовності).</p>

<select id="style" onchange="update()">
  <option value="normal">normal</option>
  <option value="italic" selected>italic</option>
  <option value="oblique">oblique</option>
</select>
<select id="variant" onchange="update()">
  <option value="normal">normal</option>
  <option value="small-caps" selected>small-caps</option>
</select>
<select id="weight" onchange="update()">
  <option value="normal" selected>normal</option>
  <option value="bold">bold</option>
  <option value="100">100</option>
  <option value="200">200</option>
  <option value="300">300</option>
  <option value="400">400</option>
  <option value="500">500</option>
  <option value="600">600</option>
  <option value="700">700</option>
  <option value="800">800</option>
  <option value="900">900</option>
</select>
<input type="number" value="20" id="size" placeholder="font-size" onchange="update()" min="0">/
<input type="number" value="1.4" step="0.1" id="height" placeholder="line-height" onchange="update()" min="0">
<input type="text" value="sans-serif" id="family" placeholder="font-family" onchange="update()">

<hr>

<div id="block">
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
  tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
  quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
  consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
  cillum dolore eu fugiat nulla pariatur.</p>
</div>

* {
  box-sizing: border-box;
  padding: 0;
}

body {
  color: #222;
}

#form {
  padding: 8px 16px;
  font-size: 19px;
}

#block {
  background: #f1f1f1;
  padding: 10px;
  font: italic small-caps normal 20px/1.4 sans-serif;
}

var style = document.getElementById('style');
var block = document.getElementById('block');
var variant = document.getElementById('variant');
var weight = document.getElementById('weight');
var size = document.getElementById('size');
var height = document.getElementById('height');
var family = document.getElementById('family');

function update() {
  block.style.fontStyle = getVal(style);
  block.style.fontVariant = getVal(variant);
  block.style.fontWeight = getVal(weight);
  block.style.fontSize = size.value + 'px';
  block.style.lineHeight = height.value;
  block.style.fontFamily = family.value;
}

function getVal(el) {
  var result = '';
  for (var i = 0; i < el.options.length; i++) {
    if (el.options[i].selected == true) {
      result = el.options[i].value;
    }
  }
  return result;
}